Hi Scott,

Positions 2 and 4 do cancel some of the hum. This one of the reasons I suspect the pickups, as I guessed that the two pickups were approaching 180° phase cancelling. Although I am not sure how the real sound gets past this.



I plugged the guitar into a small desk and fed the USB output to a Oscilloscope (PC Based). The wave forms surprised me.

While there was a fair amount of the 50-60 Hz I expected there was a weird but very regular modulation of the 50 Hz wave. When I angled the scratch plate to 90° it became a modulated almost saw tooth 50 Hz.

This led me to suspect a second (or more) noise source. One culprit was discovered - a noisy CFL globe.

Well the search continues, I need to get some copper tape to shield around the pick ups.

As the scratch plate is off the guitar I might wrap the lot in foil and ground that to see what happens. I'll put a sheet of flexible foam on the underside first, shorting it all to earth will quiet it down OK but will defeat the point of the experiment!

This is really an academic excercise, to learn a bit more about the vagueries of this shielding business...